It's recommended to have two providers, one for monthly and one block account, on two seperate backbones. I think /r/piracy or /r/Usenet has a list, and as whirlybird mentioned just add the show to sonarr and it'll eventually grab it.

If you don't have any *are suite I highly recommend getting that set up. Sonarr for tv shows, radarr for movies. It's all set and forget, just add the content you are after and the *are does the rest. You just add your indexer(s), add the provider(s) and you're sorted.

Recent stuff from big networks is more likely to get DMCA’d regularly than older stuff. As long as you add it in to sonarr you should get it eventually, but yeh unless you get it at release it can be a bit tough sometimes.

I have the same indexers as you, but I use ninja and farm for my servers. I have no problem whatsoever finding anything relatively popular from the last 20 years or so. I would look at your servers

Get a tweaknews block account. From what I know they use NTD instead of DMCA and may have the missing blocks.

For indexers I've found nzb.su to be pretty good.

the older stuff on newsdemon is hit or miss anyways cause of the way they handle their storage so it will be hard to know if its gone cause they suck or gone cause of takedown.

For clarity, are you manually downloading or using the *aar's for automated downloading?